Strain Measurements in Eastern Marginal Shear Zone of Mount Sedom Salt Diapir, Israel

Abstract

The Mount Sedom salt diapir, of Pliocene-Pleistocene age, is a vertically layered salt wall more than 2,000 m thick trending north-south parallel with the strike of the layers. The diapir head is cut by a dissolution salt table overlain by a residual caprock. Deformation features include, at greater depths, rotated boudins, stretched desiccation polygons, and fracture cleavage formed through flowage of the salt, and, at shallow depths, folded rock salt beds, folded dolomite-shale beds, and bedding-plane slip. Measurements in the eastern marginal shear zone indicate an extensional-shear distortion of 2.1--1.7 of ductile shear (probably at depth, in an early stage) recorded in the rock salt beds, plus 0.4 of slip shear recorded as displacements of the salt table at a shallow, later stage. The strain in this marginal area is considerably larger than the average for the main, inner part of the diapir. The average rate of rise for the whole diapir is 3 to 4 mm/year since the late(?) Pleistocene.